Low-level laser irradiation promotes the differentiation of bone marrow stromal cells into osteoblasts through the APN/Wnt/β-catenin pathway

OBJECTIVE: The relationship between adiponectin (APN) pathway and Wnt pathway was explored through BMSCs, and the effect of low-level laser irradiation (LLLI) on bone marrow stromal cells (BMSCs) and its mechanism were further studied. MATERIALS AND METHODS: 3-week-old Sprague-Dawley (SD) rats were selected, and mesenchymal stem cells were separately cultured and purified. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to analyze cell proliferation. After osteogenic and adipogenic induction, cultures were conducted, respectively, cells were stained with alizarin red and oil red O. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the expressions of osteogenesis-related genes, runt-related transcription factor 2 (RUNX2), and osteocalcin (OC) and those of adipogenesis-related genes, peroxisome proliferator-activated receptor-gamma (PPAR gamma) and CCAAT/enhancer-binding protein alpha (c/EBP alpha). Western blotting was used to detect the expressions of beta-catenin in the cytoplasm and nucleus. The lentiviral expression vector of adiponectin receptors (APN-R) was constructed, and the expression of APN receptor genes was silenced. The expressions of beta-catenin in APN receptors and the nucleus within cells were detected. RESULTS: LLLI promoted the bone formation by inducing the differentiation direction of mesenchymal stem cells, increasing the number of osteoblasts in the bone marrow and inhibiting the reduction of the number of adipocytes. LLLI regulates the Wnt pathway, promotes the entry of beta-catenin into the nucleus, activates the osteogenic effect of the Wnt pathway so as to promote the bone formation of osteoblasts and inhibit bone resorption of osteoclasts. LLLI promotes the entry of beta-catenin into the nucleus and the osteogenic differentiation of BMSCs through the APN pathway. CONCLUSIONS: In summary, LLLI can promote osteogenesis and inhibit adipocytes formation, thus attenuating bone resorption of osteoclasts. The mechanism of LLLI is that it promotes the entry of beta-catenin into the nucleus and regulates the Wnt pathway and the differentiation direction of mesenchymal stem cells through the APN signal pathway, thus promoting bone formation.